It has been previously known to utilize one or several venturis as an outlet from spray chambers, for instance, for spray painting automobile chassis or bodies. The venturis may be suitably disposed directly below or even at some distance from the floor of the spray chamber, which is grate-like so that conditioned air may be exhausted through it to carry away paint particles from the spray chamber. In passing through the venturis, the air speed is considerably increased causing a special effect wherein the particles of paint agglomerate and can more easily be taken care of in a subsequent separation procedure. Water is also circulated under the grate-like floor and through the venturi so that it is not stopped up by paint. The flowing water is conveyed through a collection chamber, for example to a reservoir beneath the grate-like floor and means have been provided for recirculating (either partially or completely) both the conditioned air exhausted from the spray chamber and the water.